Pulse transmitter systems



Oct 8, 1957 LA VERNE R. PHILPOTT ETAL 2,809,286

PULSE TRANSMITTER sYsTE'Ms Original F'iled April 30, 1940 8 Sheets-Sheet l ATTORNEY OGL 3, 1957 LA VERNE R. PHILPoTT Erm. 2,809,286

' PULSE TRANSMITTER SYSTEMS Original F'led Aril 30, 1940 8 Sheets-Sheetl 2 :ELST 5 PLATE CURRENT FOR TUBES 0F F/. 4.

CUFOFF /DLE HMG/Na T/ME, AB

PER/00 lE-r E VOLTAGE 0N PLATE 0F TUBE 39 .0F F/Gf AND 0F TUBE 5,9 F/G. 3, WITH SAW T0077/ AND PULSE GRID EXC/TAT/ON.

PULSE EXC/TA 770A/ VOLTAGE PULSE CHARG/N /DL E 77ME PULSE T/ME, BC

cHAHG/N T/ME, DE

D TIME PER/0D IN VEN TOR ATTORNE Od- 8, 1957 LA VERNE R. PHILPOTT ErAL 2,809,286

PULSE TRANSMITTER SYSTEMS Orgfmal Filed April 30, 1940 8 Sheets-Sheet 3 PLATE' CURRENTAN EXC/TAT/N F03 TY/QS 0F OPERATION 0F FIGURE '6.

IN VINTIR ATTORNEY Qct. 8,-1957 LA VERNE R. PHILPOTT ETAL 2,809,286

PULSE TRANSMITTER SYSTEMS original Filed April so, 1940 8 Sheets-Sheet 4 hwg/Mp Z E a. E

La lrlzeR Philpol av Rober! MPage AT1-omver'- T/ME, a PULSE T/ME 1- OCLYS, 1957 LA VERNE R. PHILPoT-r ET AL 2,809,286

PULSE TRANSMITTER SYSTEMS 8 Sheets-Shea?l 6 Original Filed April 30, 1940 on 9 mM n mnt. Naw m M E Vb T R vao 1 m .mLR A ms mm W. QW ,w D@ ya F M n. Elf; l. 7 X .M7 M M|||U 5| 5W w y Pa c :mlml e A F E i 1T. m aw m A 00, Il NIEC f f N A NK G M n M m M alix M u w c o P, i i, 2 m 8 6 4 2 +0 8 Sheets-Sheet 7 La Mami? R Philpol BY- Robert M .Page

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PULSE TRANSMITTER SYSTEMS LA'VERNE R. PHILPOTT ETAL Oct. 8, 1957 original Filed April so, 1940 PULSE TRANSMITTER SYSTEMS Original Filed April 30, 1940 8 Sheets-Sheet 8 m m" '4 ,XT '46 |47 L3' |44j RECENER LA VERNE R. |=|||LR0TT ROBERT M. PAGE ATTORNEY5 PULSE TRANSMITTER SYSTEMS La Verne R. Philpott, Caldwell, N. J., and Robert M. Page, Camp Springs, Md.

Original application April 30, 1940, Serial No. 332,526. Divided and this application March3, 1952, Serial No. 274,643 v 8 Claims. (Cl. 250-17) (Granted under Title 35, U. S. Code (1952), sec. 266) This application is a division of our application for Pulse Transmitter Systems, Serial No. 332,526, filed April 30, 1940, now abandoned.

This invention relates to high frequency pulse transmitting apparatus and more particularly to means for supplying power at high levels and means for keying the system, the same general principle being applied to both Y vacuum tube and spark transmitters.

Among the several objects of this invention are:

To provide simple and economical means of setting up a very short pulse of radio frequency energy of high intensity; Y

To provide means for supplying pulsing energy to a large transmitter from a relatively small source;

To devise a spark transmitter that is self-pulsing.

In the drawings:

Fig. l depicts our invention embodied in a system wherein the voltage of the plate voltage of the transmitter tube is equal to the voltage of the plate power supply, the transmitter keying voltage being supplied by energy stored in accordance with this invention;

The apparatus in Figs. 2 and 3 is in general similar to Fig. l except that the supply voltage is less than the operating voltage of the transmitter tube.

Fig. 4 shows graphically the variations of plate voltage on the transmitter tube in the systems of Figs. 2 and 3 and on the keying tube in Fig. l;

Fig. 5 is a graph depicting the plate current of the transmitter tube in Fig. 3 and keying tubes in Figs. l

and 2.

Fig. 6 is similar to Fig. 4 but illustrates dierent types of excitation;

Fig. 7 shows the plate current and excitation when the conditions correspond to those in Fig. 6;

Fig. 8 illustrates another embodiment of our invention wherein the system is self-keying;

Fig. 9 shows a still further and more efficient embodiment of our invention;

Figs. 10 to 21 are graphs illustrating the variations of potential at various points in the system of Fig. 9;

Fig. 22 depicts the form of invention in Fig. 9 associated with a sweep circuit, a cathode ray tube and the receiving apparatus for echo rangingor similar purposes;

Fig. 23 shows our invention applied to a self-keying spark transmitter, associated withcathode ray tube indicating means, as in Fig. 22; and

Fig. 24 is a detail of the spark transmitter mechanism.

There are numerous applications of high frequency radiant energy that require a short pulse, such as radio echo ranging, etc. The production of such a pulse is difficult because of the extremely short duration of the pulse that is required, in some cases as little as l0"1 seconds. Another difficulty is the necessity of radiating a high peak power, say 1S kilowatts, which is complicated by the fact that there must be no appreciable radiation at or near the radio carrier frequency or any of its sub-harmonics during the interval between pulses.

As a general illustration of our present invention we will cite the case of a self-oscillating circuit to whichV is continuously applied plate potential of the value required for operation and a negative grid bias capable of extinguishing oscillations, except during those inter-V vals when it is removed to permit radiation of a pulse. The transmitter may consist solely of this stage or it may have additional power amplier stages. This type of circuit is shown in Fig. l wherein the tube 27 is the transmitter tube whereof the anode 28 and grid 29 are connected by the parallel oscillatory circuit 30 and 33 and capacitance 31. The energy radiated by tube 27 s supplied by source 32 having its positive terminal connected to inductance 33 of oscillatory circuit 30 and 33 and its negative terminal connected to cathode 34 of tube 27, a capacitance 35 being connected in parallel across source 32. Negative bias sufficient to block Vtube 27 is applied to grid 29 by source 36 through resistance 37 and grid impedance 38.

Tube 39 isa power pentode biased for class B operation, having its control grid and screen grid connected together for high Asimplification factor, and its suppressor grid 40 connected to source 36 at 45 volts positive to lower the plate voltage during the charging time DE, Fig. 4. The screen and control grids of tube 39 are connected through grid current limiting resistance 41 to source 42 that applies a negative bias to these grids, therev being included in the grid circuit the secondary y 43 of a transformer 44 for applying keying voltages.

former 44, the screen and control grids of tube 39 are swung positive and a heavy current flows from source 36 through inductance 45 and tube 39, with resultant storage of energy in inductance 45. When the grids of tube 39 go rapidly negative, the energy stored in Vinductance 45 is released by the collapse of the electromagnetic iield and, since tube 39 is again blocked, this energy ows through lead 46, capacitance 47 and resistance 37, thereby impressing a high positive potential on grid 29 of tube 27 that unblocks tube 27 and permits current to flow through tube 27 with the resultant generation of oscillations in oscillatory circuit 30 and 33, which oscillations are filtered by tuned circuit 48 coupled to circuit 30 and 33 and radiated by antenna 49.

Referring now to Fig. 4, the time DE is the interval dur-V ing which tube 39 is conducting and is storing energy in inductance 45, practically all of the applied voltage 36 being dropped across inductance 45. As the current through the pentode 39 increases, the anode potential thereof rises along the Ep-Ip curve characteristic of the tube. At the time A or E, Figs. 4 and 5, the instantaneous voltage applied to the grids of 39 is rapidly becoming negative and has reached the point at which any further increases of plate current would resultV in a very sharp increase in plate voltage. At thls instant, the energy stored in inductance 45 is 1/2LIo2. The Vtime interval AB, called the cut-ott time, is that portion of the cycle during which the grids of tube 39 change from the full conduction potential to full cut-ott and should be as shortv as possible.

When cut-off occurs, the energy stored in inductance grid input impedance of tube 27 and capacitance 31.V Designating all the capacitances involved` as C, then the system will charge to some potential until 1/2LI02=1/2CE02 and this will occur in 1A cycle of a frequency as determined 'gf by the product LC, VWhere L designates the value of in- Patented Oct.u 8, 1957-` it is dissipated in circuit resistance, of which 37 is the major part. Should any appreciable oscillating energy exist in inductance 45 at the time D, when tube 39 is again made conducting for charging inductance 45, it will be quickly damped by the reduction of plate resistance of tube 39. If the grid of tube 27 draws current at a potential lower than that to which the combined capacitanceC would finally charge, the remainder of the energy will be dissipated at that level. This condition is represented by a fiat top on'the oscillation peak, as in Fig. 6, BC.

It is apparent that the longer the charging time the more energy can be delivered at aV particular supply voltage and pulse frequency. By altering the grid excitation from sine wave to vertical saw tooth or negative pulsing, the proportion of charging to discharging time can be altered say to a ratio of to l instead of 1 to 1, as in the sine wave type. These modes of operation are illustrated inv Figs. 6 and 7, wherein the notation is the same as in Figs. 4 and 5. While tube 39y is shown as a pentode for best practical operation, a triode or tetrode can be substituted and work equally well provided the grid' is properly controlled.

The polarity of the pulse derived from inductance 45 is such as to oppose the action of bias potential 36 with the result that, for the time BC, Fig. 4, thetransmitter tube is not blocked and will oscillatenormally. It is evident that when tube 27 is operated in the manner described', the average power dissipation is much lowerA than would be for continuous transmission and, as a result, tube 27' can be operated at extremely hi-gh instantaneous outputs. A tube rated to operate continuously at 2,000 volts will operate at 5,000 to 10,000 volts while pulsing, so far as dissipation is concerned. One feature or disadvantage in the system of Fig. 1 is the unavoidable large size of source 32, which becomes the largest physical part of the system.

Fig. 2 depicts a system wherein the energy for the pulse is derived from a source 50 of much lower potential than that at. which the pulses are radiated. The cathode 5l of tube 52 isy connected to the positive terminal of source 50 and the grid 53 is connected to the negative terminal thereof through radio frequency impedance 38, resistance 54: and capacitance 55. The positive terminal of source 50 is likewise connected through storage inductance 45 to the anode of tube 39 and, through lead 56, to inductance 33 of oscillatory circuit 30 and 33, the capacitance 57 being in parallel with inductance 45.

When tubey 39 is rendered conducting by al positive half cycle through transformer 44, energy is stored in inductance 45t, the anode voltage of tube 39 rising along its characteristic curve as above described. When tube 39 is again blocked, the energy stored in inductance 45 discharges into capacitance 57 until the latter is charged to a potential suiciently great that, applied` to the anode of tube 52, it overcomes they blocking bias and permits energy in capacitance 57 to discharge through tube 52 with concomitant generation and radiation of a. pulse of high frequency energy. When the energy transferred to capacitance 57 from inductance 45 is dissipated, the anode potential on tube 52 drops, the tube again blocks, and the pulse is complete.

It may be readily shown that with. the sourcey 50 having a vol-tage of 1,000 volts, inductance 45 having a value of 0.407 henry, a maximum charging current through tube 39 of 0.7 ampere and the other elements of the system having such valuey as to give a pulse frequency of 3,000 per second, the level at which radiation occurs is in the vicinity of 10,000 volts. It mayv further be shown that if the stored energy is discharged in 5 microseconds, the pulse power input is 20 kilowatts but if it be dissipated in 2 microseconds, the power reaches 50 kilowatts.

The apparatus shown in Fig. 3 differs somewhat from that shown in Figs. 1 and 2, although the general principle is the same. Here, the tube 59 serves the double purpose of controlling the storage of energy and generating the radio frequency oscillations, the tube 60 being merely a keying tube to provide excitation for grid 61 of tube 59. It will be noted that the positive terminal of source 62 is connected to the anode of tube 59 through storage inductance 45 and the negative terminal thereof is connected to the cathode of tube 59, the capacitance 63 being connected at one side to a point between oscillatory circuit 30-33 and inductance 45 and to the other side at the cathode of tube 59. Under these conditions current will flow through tube 59 and inductance 45 with the resultant storage of energy in inductance 4S, since grid 61 is connected through resistance 64 to a point of positive potential on source 62 but no oscillations will be generated because grid 61 is at a potential more positive than the plate. When a keying impulse is applied through transformer 44 to grid 65 of tube 60, this tube draws current and the resulting drop in potential across resistance 64 Vis applied to grid 61 and momentarily blocks tube 59, whereupon the energy stored in inductance 45 is discharged into capacitance 63, which is thereby charged to a high voltage. Radio frequency oscillations will occur when the anode potential rises high enough to unblock tube 59 against the applied negative grid bias across 64, and will continue until condenser 63 is substantially discharged and tube 59 becomes again blocked. When tube 60 again blocks after the cessation of the keying voltage on grid 65, tube 59 unblocks with low anode potential and energy is againV stored in inductance 45.

Even if tube 59 does not become completely blocked, still its plate potential is forced very high by impressing a high negative potential ongrid 61 which gives rise to a transient high powered radio pulse. Under certain conditions tube 59 may not completely eea-se oscillating at the desired radio frequency during the charging time, yet there still will exist a large difference in the radiated power between steady and pulse conditions.

It is apparent that if tube 60 and the elements immediately associated therewith are omitted, the apparatus in Fig. 3 will become self-pulsing, the blocking of tube 59 beingv effected by the drop of potenital in resistance 64 due to ilow of rectified grid current therethrough.

In the case of Fig. 3, as also in those of Figs. l and 2, the introduction of a saw tooth or pulse excitation on the grid of tube 60 instead of sine wave excitation will facilitate a higher powered pulse for the same pulse frequency and supply volts available, since the more abrupt wave front will effect the change in conductive condition in a shorter time. This is evident from. a comparison of Figs. 4 and 6, wherein it is seen that the idle time CD is much less when saw tooth or pulse grid excitation is employed as in Fig. 6 instead of the sine wave excitation in Fig. 4. This allows a longer charging period with a possible increase of either the inductance value 45 or the final plate current of tube 39 or 59, namely lo.

Fig. 7 shows graphically the relation between the excitation` voltage and the plate current in the apparatus of Figs. 1, 2, and 3 when saw tooth and pulse grid excitation, respectively, are applied. It is believed that the captions of these figures of the drawings render detailed discussion thereof unnecessary.

Fig. 8 illustrates another self-keying pulse transmitter embodying the energy storage principle of the present invention. Here the grid 61 of transmitter tube 66 has applied to it a blocking potential from the source 67. The ano'des. of transmitter tube 66 and of charging tube 68 are connected to the positive terminal' of source 69` through storage inductance 45, whilethe anode of keying tube 70 yis connected to the positive terminal of source 69 through resistance 71. source 69 throughinductance 45 and stores upenergy in the inductancethe potential on the anode of tube 68 risinggradually until the current reaches a critical value, tube 70 meanwhile being blocked by cathode self-biasing circuit 70. However, when the current through tube 68 reaches thecritical value, the anode potential thereof risesvery quickly and this rise in potential is transmitted throughcapacitance -72 to grid 73 of tube 70 and unblocks tube 70. n

`The'iiow'of current through tube 70 gives rise to a drop in potential across resistance 71 which is impressed upon the grids of tube 68 and blocks this latter tube. The energy stored in inductance 45 is thereupon transferred to capacitance 74 and when the potential thereof, which isimpressed upon the anode of tube 66, rises toa suicient value tube 66 is unblocked yand the energy in capacitance 74 is discharged through tube 66and 4oscillations at high power level and high frequency are generated. The dissipation of the energy stored in inductance 45 results in the blocking of tube 70 and the tube 68 lagainpasses current. It is apparent that this is a self-keyingtransmitter system.

If extremely high peak power is required from the radio transmitter the energy stored vin inductance 45 must be transferred to capacitance 74` before the pulse begins, else the peak average plate current of tube 66 cannot exceed the peak current in tube 68 and this imposes La `serious limitation upon the maximum applied voltage.` Simply to transferthe energy from inductance 45 to capacitance 74 prior to the radio pulse and then to permit capacitance 74 to discharge through tube 66 would result in an unduly long pulse and a large change of appliedgpotential throughout the operating period.

Tube 68 `draws current from Particularly at the higher carrier frequencies, the frequency depends so largely upon applied potential that a 100% change in applied voltage may result in ya fre- Y quency change as large as 2%. When reception of such a signal by heterodyne receivers is attempted, circuit selectivity handicaps the system. It has been determined, however, that the frequency remains practically constant when plate potential is held fixed and the generation of the oscillations and discharge of the stored energy are controlled by changes of potential on the grid of the transmitter tube.

A system wherein the transmitter tube is unblocked V by changes in grid Vpotential is shown in Fig. 9. While this is illustrated `as Vbeing an extremely-high frequency system, this is-not essential. The two transmitter tubes 75 have` anodes 476 connected in high frequency pushpull, and delivering power through the high frequency tank circuit totheantenna 77 and their grids 78 connectedin high frequency push-pull and through resistances 79 `and 80` to the negative terminal of source 81, the cathodes `SZibeingsupplied through high frequencyV push-pull impedance 83 from a transformer secondary 84.

Energy for generating-the pulses is drawn from source 85 through storage inductance 45 and power pentode 86 having its three grids 87 connected together and its cathode. 88fconnected to the negative terminal of source 85 and 'to ground, Vthe grids 87being connected through impedance 89 to a point 100 volts positive on source 85. Anode 90 of blocking tube 91 is also connected to the 100 volts positive point on source 85 through impedance 89, the cathode 92 of tube 91 being connected tothe negative terminal of source 81 through capacitances 93 in parallel with variable resistance 94` Capacitance 95 is connected at one side to a point between inductance 45 and anode 96 of tube 86 and at its other sideto a time constant resistance 97 that is connected through transformer secondary 43 to the negative terminalof source 81.' Capacitance 98completes the circuitv forthe synchronizingpulses applied throughtransformer 'Grd` resistance 99 is connected to a point between capacitance and resistance 97 and to grid 100 of blocking tube 91 and is bypassed by a small capacitance 101. A variable capacitance 102 is connected in parallel with storage inductance 45, and the terminals of inductance 45 and capacitance 102 that are connected to anode 96 are connected to the anode 103 and grid 104 of a'rectifier tube 105 whereof the cathode 106 is con-l V-nected to storage capacitance 107 that supplies energy to anodes 76 and cathodes 82, respectively, of transmitter tube 75 through leads 108 and 109, respectively. It is to be understood that capacitance 107 is much larger than the analogous capacitances of the previously described systems. A safety gap 110 is connected across storage capacitance 107.

Anode 111 of'keying tube 112 is connected through leads 113 and 114 to the positive terminal of source 85 and the cathode 115 thereof is connected through resistance'80 and lead 116 to the negative terminal of source 81 which is in series with source 85. Tube 112 is a pentode having its grids 117 connected togetherv and, through lead 118 and capacitance 121, to the anode 103 'of rectiiiertube 105 and likewise to the anode 96 of tube 86. A reduced pressure safety gap 119 is connected between grids 117 and cathode 115 of keying tube 112.

The operation of this form of our invention is as follows: After one cycle of operation, the cathode 92 of tube 91 is held positive by the charge on capacitances 93 and hencetube 91 is blocked and draws no current.

comitant storage of energy therein and the voltage on anode 96 will rise along the Ep*Ip curve of tube 86 untll a critical value of current is reached, when the voltage on -anode 96 will increase very rapidly. This `pulse of positive voltage is transmitted through capacitance 95 and small capacitance 101 to grid 100 of blocking tube 91 which is draw current through drop through'impedance 89 is applied to grids 87 of charging tube 86. 95 must charge through time constant resistance 97 and the duration of this charge is given such value that tube 91 is held conducting, and thereby tube 86 is held blocked,

until the energy stored in inductance 45 is transferred through rectifier tube 105 to storage capacitance 107, the f Irectifier 105 having been rendered conducting by the high positive potential developed on the anode 96 of tube 86. The purpose of rectifier tube 105 is to prevent the high potential of storage capacitance 107 working back into the other elements of the system.

As soon as -the potential on anode 96 begins to increase rapidly, a positive pulse is impressed upon grids 117 of keying tube 112 through lead 118 and capacitance 121, which unblocks keying tube 112 and the resultant iiow of current through tube 112 and resistance 80 in series therewith gives rise to a positive potential that i is impressed upon grids 78 of transmitter tubes 75 through p smallV capacitance 122, thereby transiently unblocking transmitter tubes 75 and permitting the discharge of energy from storage capacitance 107 through theetransn;

mitter tubes` 75, with the concomitant generation of a very short pulseof extremely high frequency energy at a higlrpower level, the pulsebeing radiated from an-.

teuna 77. It is to be understood that the generation and thereby unblocked and begins to impedance 89, and the resulting i Capacitance radiation of the pulse take place during the rise of potential on anode 96 and that the pulse is substantially complete before rectifier 105 has become conducting to transfer to storage capacitance 107 the energy in storage inductance 45. The transmitter tubes 75 in Fig. 9 being grid voltage controlled, objectionable frequency changes arising from anode voltage control are eliminated.

By way of example, if inductance 45 have a value of 0.407 henry, the pulse frequency be 3,000 pulses per second and theV peak current through inductance 45 be 0.7 ampere, the energy stored per cycle is 1/zLlo2 or 0.10 joule. If the integrated value of capacitances 95, 102 and 121 be 350 micromicrofarads, the peak voltage to which capacitance 107 would charge in the absence of any drain would be 23,900 volts.

Consideration of the graphs in Figs. 10 to 21 will aid in understanding the sequence of voltage and current conditions in various parts of the system of Fig. 9 during a cycle. Referring first to Fig. 10, the charging time a is that interval during which the tube 86 is passing current and storing up energy in the storage inductance 45. When the critical value of current is reached and the potential on anode 96 begins to rise rapidly the impulse of positive potential is transmitted through lead 118 and capacitance 121 to the grids of tube 112 giving rise to the pulse which is designated by b in Fig. 10. It will be noted -that this is very short and occurs during the rapidly rising anode potential. The discharge time c is the interval during which the energy is being transferred from inductance 45 through rectifier 105 to capacitance 107, and the collapse or idle time d is the interval during which the potential on anode 96 is dropping. It will be observed that the potential of anode 96 reaches a value in excess of l kilovolts.

Fig. 11 shows the excitation potential at the junction of resistances 99 and 97, while Fig. 12 shows the actual grid excitation of tube 91. It will be understood that when a very high positive excitation is applied to grid 100 this grid will tend to draw a heavy grid current which would charge condenser 95 too rapidly, and consequently resistance '99 must be of suilicient value to hold this current to an allowable value.

Fig. 13 shows the excitation between grids 117 of tube 112 and the negative side of source 81 while Fig. 14 illustrates the net effective voltage on the grids o'f tube 112. It will be observed in Fig. 14 that the maximum positive voltage ongrids 117 is 100 volts and consequently setting safety gap tube 119 to discharge at 200 volts allows an ample margin for voltage variation during operation and yet the tube will be protected against negative potential swings on the grids 117 sutliciently great to damage the same. If tube 112 is sufficiently well insulated to withstand the full excitation, tube 119 may be eliminated with no effect on the operation save that it will require a longer time for condenser 121 to discharge through resistance 120.

Fig. l depicts the grid potential on tube 86. Fig. `16 depicts graphically the potential developed across resistance 80 yby the ow of current through tube 112 and consequently the voltage applied to grid 78 of transmitter tubes 75. Fig. 17 shows the drop across resistance 79 due to grid current from the transmitter tubes 75, While the net operating potential on transmitter grids 78 is shown -in Fig. 18, the resultant amplitude of the radio frequency pulse being plotted in Fig. 19. Y

Fig. 20 shows the small ripple voltage across capacitance 107 due to discharging through tube 75 wand the charging through tube 105 where capacitance 107 has a value of 1/3 microfarad and the peak of transmitter input power Vis l5 kilowatts.

Fig. 22 illustrates the form of our invention described inconnection with Fig. 9 associated with A-a receiver, -a cathode `ra'y tube and suitable sweep circuits rfor `the cathode ray tubeto utilize our invention inecho ranging work. The elements in '.Fig. l22 lthat are t common 'to 4this ligure and Fig. 9 are designated by the same reference characters. Tube 123 is a pentode connected for high current capacity and is blocked the greater p-art of the time by positive potential due to a charge residing on capacitances 124 and 128 to which cathode 125 is connected by lead 126. However, when the potential on anode 96 of tube 86 begins its rapid increase a positive potential is impressed upon grids 127 of tube 123 that unblocks tube 123 and permits a quantity of electrical energy to pass through tube 123 and be stored in capacitances 124 `and 128. This moves the spot on the screen of cathode ray tube 129 to its initial position simultaneously with the unblocking of transmitter tubes and the transmission of the pulse. The charge on capacitances 124 and 128 flows off through tube 130 which is so connected as to constitute a constant current device and hence the .potential on capacitances 124 and 128 decreases at a uniform rate and the spot is moved linearly across the screen of cathode ray tube 129. If the transmitted pulse is reflected by a distant body, the reflection is picked up by antenna 131 and is suitably amplified in a receiver 132 whereof the output is connected to plate 133 of the cathode ray tube 129 to move the spot at right angles to the motion thereof effected by the potential on capacitances 124 and 128.

The screen of the cathode ray tube 129 may be calibrated in terms of distances whereby the point of detiection of the cathode ray beam by a signal from receiver 132 will indicate the distance to the reflecting object, as is well known in this art. The capacitances 124 and 128 constitute `a potential divider .and their values are so chosen that the etect thereof on the beam in cathode ray tube 139, exerted through plate 134, moves the spot as desired. Plates 135 and 136 of cathode ray tube 129 are connected by leads 137 and 138, respectively, to the variable resistances 139 and 140 to adjust the initial position of the cathode ray tube spot. Receiver 132, for satisfactory functioning, must be of a type specically adapted for the ultra high frequencies employed and should have a very high amplifying power to make possible the reception of extremely faint echoes from remote Objects, and may be like the receiver shown in the application of Leo C. Young and Robert M. Page, Serial No.

223,502, filed August 6, 1938, now Patent No. 2,554,515.

Fig. 23 is a schematic diagram of a spark type transmitter supplied with energy for transmitting pulses by means off energy stored as above described. Due to the [fact that several of the elements in this ligure have functions identical with those of corresponding elements in Fig. 9, the same reference characters will be applied. Tube 86 is a pentode that draws energy from source 140 through storage inductance 45 and the rise of potential on anode 96 is transmittedV through capacitance 95 and capacitance 101 .to grid 100 of blocking tube 91 that is normally held non-conducting by positive charges on ycapacitances 93 connected in parallel with resistance 94 to cathode 92. The grid resistance 99 and time constant resistance 97 are the same as in Fig. 9. When tube 91 is .rendered conducting it draws current through inductance 89 and the potential drop resulting is applied to grids 87 of tube 86 to block the charging tube 86. Capacit-ance 141 is sufficiently large to conduct freely the alternating current components of anode cathode cur- Y rent of tube 91.

When tube 86 is blocked the energy stored in induct- I ance 45 is discharged through lead 142 to interior concentric line member 143 and lead 144 to exterior conouter end of the exterior member 145 to constitute an effective radiator.

It will be noted that the concentric line members 143 Fig. 9. To insure proper extinction offthe lspark across gap 146 and `to deionize Ythe -air toprevent premature" discharge, a pump 149 may lbe provided to blow air through the hollow center of spark terminal 147. The high positive potential yon `anode 96 may be transmitted by lead 15) and capacitance 151 to synchronize sweep circuits of cathode ray tube 129 with the transmitted pulse whereby the distance of -a reflecting object may be determined by the echo therefrom received by means of antenna 131 and receiver 132, as described in connection with Fig. 22. The length of the pulse on the spark transmitter in Fig. 23 will be effectively determined by the decrement of the system.

The invention described herein may be manufactured and/or used by or for the Government of the United States of America for governmental purposes without the payment of `any royalties thereon or therefor.

What is claimed is:

1. A high frequency pulse transmitter, comprising a discharge device and elements connected thereto to constitute a self-oscillatory system, said system being normally blocked; a source of current, and in -series therewith an electronic discharge device capable of being selectively rendered conducting or non-conducting and an energy storage element to store energy when said device is conducting; means to render said device recurrently conducting or non-conducting, and means to transfer to said system when said device is non-conducting the energy stored in said element as energization pulses, to unblock said system and generate a discrete multiple cycle wave train during each energization pulse only during a minor portion of the recurrence period.

2. A radio frequency impulse generator comprising energy storage means responsive to current iiow therethrough to progressively store energy, recurrently operative electronic control means initiating current ow through said first-named means and abruptly terminating said current iiow after a predetermined interval, means discharging said stored energy immediately following said predetermined interval into a circuit characterized to absorb said energy during a time interval extremely short relative to said predetermined interval and means responsive to said discharged energy to generate a discrete multiple cycle radio frequency impulse only during said extremely short time interval.

3. A pulse generator comprising a source of direct current, an inductor, a capacitor, a load circuit having an asymmetrical conduction characteristic, a charging circuit having an asymmetrical conduction characteristic coupling the capacitor with the inductor and so connected in shunt to said load circuit as to provide a path for current in the direction opposite to that provided by said load circuit, control means for periodically causing a current to flow from said source through said inductor to store energy therein and interrupting said flow of current whereby said energy is transferred to said capacitor through said charging circuit, and switch means periodically operative in definite time relation to operation of the control means to discharge energy thus stored in said capacitor through said load circuit.

4. In a system for producing recurrent pulses of ultra high frequency oscillations employing an oscillation generator having a cathode and an anode, a circuit for producing recurrent pulses of direct current through thecathode-anode path of said generator to cause the production of ultra high frequency oscillations comprising a direct current source, an inductor, an electric discharge device having a space path, a control electrode therefor and so 10 V connected that current from said source may ilow through said space path to saidinductor, ymeans for periodically varying the voltage of said control electrode to alternately cause said space path to be conductive whereby energy from said source is stored in the-magnetic iield of said inductor and to block said space path, a capacitor connected in circuit with said inductor whereby Vthe energy stored in the magnetic field of said inductor is transferred to the electrostatic eld of said capacitor when said space path is blocked, and switching means for discharging the energy stored in the dielectric field of said capacitor through the anode-cathode path of said generator, said switching means comprising a second electric discharge ydevice having a control electrode normally biased to block the space path thereof, and means controlled in definite time relation to the blocking of the space path of said first mentioned electric discharge device for impressing a positive voltage on said control electrode to trigger off said second electric discharge device.

5. A transmitter for high frequency pulses comprising a source of direct current power, power pulse forming means connected with the power source recurrently operative to generate power pulses, unilateral impedance means connected with the power pulse forming means for conducting said pulses, capacity means receiving the pulses from the unilateral impedance means, a high frequency oscillator energized by the capacity means, and oscillator control means recurrently operative at the recurrence rate of the power pulse forming means to operate the oscillator only through a minor portion of each recurrence peri-od and to block oscillation of the oscillator during the rest of the recurrence period to generate a high frequency pulse wave train during each period.

6. A transmitter for high frequency pulses comprising a source of direct current power, power pulse forming means connected with the power source recurrently operative to generate power pulses, unilateral impedance means connected with the power pulse forming means for conducting said pulses, capacity means receiving the pulses `from the unilateral impedance means, a high frequency oscillator energized by the capacity means, and oscillator control means operative synchronously with the power pulse forming means to block oscillation of `the oscillator throughout conduction of the unilateral impedance and to operate the oscillator to generate only a relatively short high frequency pulse at another phase of each recurrence period.

7. A transmitter for high frequency pulses comprising a source of direct current, inductance means, switch means recurrently operative to connect the inductance means across the source for a charging interval and thereafter disconnect the same to generate a power voltage pulse, unilateral impedance means connected with the inductance means for conducting said pulses, capacity means receiving said pulses from the unilateral impedance means, a high frequency oscillator energized by the capacity means, and oscillator control means recurrently operative at the recurrence rate of the switch means to operate the oscillator only through a minor portion of each recurrence period and to block oscillation during the rest of the recurrence period to generate a single high frequency wave train pulse during each period.

8. A high frequency discrete pulse transmitter comprising a source of direct current, inductance means, switch means recurrently operative to connect the inductance means across the source for a charging interval and thereafter disconnect the same to generate a power voltage pulse, a normally inoperative high frequency oscillator, and a feed circuit coupling the oscillator with the inductance means to apply recurrent energization pulses to the oscillator in denite time relation to operation of the switch means, the oscillator comprising circuit means operative under the pulse energization to effect generation of a multiple cycle high frequency wave train during each energizaton pulse and tolerminate: oscillaton operation, substantially synchronously Withltheaend lof each venergi`` References (iteddnV the v111e of-ths patent UNITED STATES PATENTS f Hisngj June 5, 1928 Fearing Dec. 11, 1928 Be'thenod` Dec. 15, 1931 Luck' Apr. .5, 1938 SchlesingerV Nov. 22, 19384 

